What does the physical and chemical properties of ink refer to?

The physical and chemical properties of ink manufacturers mainly refer to its density, fineness, transparency, gloss, light resistance, heat resistance and acid, alkali, water, solvent (alcohol) resistance.

Density refers to the weight of ink per unit volume at 20 ° C. It's called g/cm3. The density of the ink is determined by the type and proportion of raw materials used in the ink, and is affected by the external temperature. The density of ink has a certain relationship with the printing process. The density of the ink is related to the amount of ink used in the printing process. Under the same printing conditions, the amount of ink with high density is greater than that of low density ink.

The density of the ink is too large, mainly because of the high density of the pigment in the ink. In the printing process, because the binder can not drive the pigment particles with excessive density to transfer together, the solid particles such as pigments accumulate on the ink roller, plate, or rubber sheet surface, forming a blocking phenomenon. Especially in high-speed printing or when the ink is thinner, the use of dense ink is more likely to occur. At the same time, when the high density ink is mixed with the low density ink, if the gap between the two is too large, it is easy to produce ink stratification. The ink with low density floats, and the density sinks, so that the color of the ink surface is biased toward the ink with low density, and the color of the ink at the bottom is biased toward the ink with high density. Under normal circumstances, the density of printing ink is between 1g/cm3 and 2.25g/cm3.

Fineness refers to the degree of dispersion of solid powder such as pigment and filler in the ink in the binder, also known as dispersion. It indicates the size of the solid particles in the ink and the degree of distribution of the particles in the binder. The fineness of the ink indicates the fine of the solid particles, and the distribution of the solid particles in the ink is uniform. The fineness of the ink depends on the wetting degree of the binder to the pigment and other solids and the fineness of the ink after the ink mixing and rolling.

The fineness of the ink is related to the rheology, fluidity and stability of the ink, and is a very important quality index. The fineness of the ink is poor, the particles are coarse, and the blocking phenomenon will be caused in printing. In lithography and gravure printing can cause damage to the plate and scraper phenomenon. And because of the uneven dispersion of the pigment, the intensity of the ink color can not be fully developed, affecting the coloring power of the ink and the brightness of the ink film after drying.

Transparency refers to the degree to which the ink refracts the incident light (transmission). Transparency in printing refers to the degree to which the ink can withstand the underlying color of the object when it is evenly coated into a film. The transparency of the ink is low, and when the base color cannot be fully displayed, the base color will be covered to a certain extent, so this performance of the ink is also called the hiding power. The transparency of the ink is inversely proportional to the hiding power, and the transparency is expressed by the thickness of the ink layer when the ink completely covers a certain background color, the greater the thickness, the better the transparency of the ink and the lower the hiding power.

The transparency depends on the difference between the refractive index of the pigment and the binder in the ink, and is related to the dispersion of the pigment. The smaller the refractive index difference between the pigment and the binder, the better the dispersion of the pigment in the binder, the higher the transparency of the ink.

Gloss refers to the ability of the ink on the surface of the print to concentrate and reflect light in the same direction when the ink is dried. High gloss inks show high brightness on printed matter. The gloss is mainly determined by the type and nature of the binder in the ink, the treatment of the refining process in the ink manufacturing, and the flatness of the ink film after drying. In addition, the gloss of the ink is also affected by the nature of the pigment in the ink composition, the size and shape of the particle and the dispersion; The influence of ink permeability, leveling, dryness and other properties; The impact of the substrate and so on.

Light fastness refers to the ability of ink to change color without changing under fluorescent lamp irradiation. The light fastness of the ink indicates the degree to which the print fades or discolors under light exposure. Although the printing ink with strong light resistance is irradiated by sunlight for a long time after printing, the degree of fading of the printed matter is small; The printing ink with poor light resistance is easy to fade, and even the color will fade completely. In the classification of ink, grade 8 is the least easy to fade, and light resistance is preferred. The light resistance of the ink depends mainly on the pigment. The light resistance of the ink has no effect on the printing process, mainly related to the use of printed matter.

Heat resistance refers to the ability of the ink to not change color when heated. The strong heat resistance indicates that when the print is heated to a higher temperature, the ink will not produce discoloration. The heat resistance of ink mainly depends on the type and performance of pigment and binder. Some pigments not only change color when heated, but even change.

This performance refers to the ability of the ink to change color and performance under the action of acid, alkali, water, alcohol or other solvents, also known as the chemical resistance or resistance of the ink. The chemical resistance of the ink is strong, and under the action of acids, alkalis and other substances, the color and the nature of the ink will not change. The chemical resistance of the ink is determined by the type and performance of the pigment and binder, and is related to the state of the combination of the pigment and binder, and is related to the stability of the ink.